The present invention relates to equipment for threading caps onto bottles and the like. More particularly it relates to equipment which has a more wear resistant linkage in a portion of a capping head that accommodates both rotational and axial movement of a clutch of the capping head.
It is known to use automated capping equipment to apply threaded caps to pre-threaded bottles (e.g. in the beverage industry). Such equipment is typically provided with a clutch that permits enough rotational torque to cause the cap to be threaded tightly on a bottle, yet which prevents too much rotational torque from being applied (as would lead to stripping of the bottle or cap threads). See e.g. U.S. Pat. Nos. 4,364,218 and 4,599,846.
Such clutches are preferably of the hysteresis type in which two essentially ring-like arrays of magnetic material sandwich a hysteresis material between them. The relative position of one magnetic ring structure with respect to the other determines resistance to rotational torque. See e.g. U.S. Pat. Nos. 4,674,264 and 7,181,892.
In connection with such equipment the capping head is mounted on a drive shaft for rotation therewith, with the cap to be threaded on the bottle positioned at the bottom of the capping head. As the cap is threaded down onto the threads of the bottle by the capping head, there must be provision for the capping head to accommodate the axial movement of the cap while still driving the cap rotationally.
Most typically this is achieved by having a rotational drive sleeve (that is driven by the drive shaft) have mounted on it a spring. A lower housing part “floats” axially in with respect to the driven sleeve due to the spring bias. There is conventionally a linkage between the driven sleeve and lower housing to cause the driven sleeve to rotate the lower housing while also permitting this axial floating.
This linkage typically involves use of pins, splines, flats or keys acting as the linkage between the two parts. See e.g. U.S. Pat. No. 7,181,892. However, this can lead to significant wear at the linkage even if lubrication is periodically added at that point. Further, providing a means to add such lubrication periodically adds cost and requires customers to stop production lines for this maintenance (and remember to do so).
It has proven difficult to reduce the incidence of such problems without introducing still other concerns. Thus, a need still exists for improved capping heads which better address these concerns.